Moist fuel furnace



Dec. 19, 1967 R. w. JONES 3,

MOIST FUEL FURNACE Filed 001:. 20, 1965 4 Sheets-Sheet 1 I NVENTOR.

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R. W. JONES MOIST FUEL FURNACE Dec. 19, 1967 Filed Oct. 20, 1965 UnitedStates Patent 3,358,625 MOIST FUEL FURNACE Robert W. Jones, Birmingham,Mich, assignor to Bagelow-Liptak Corporation, Detroit, Mich., acorporation of Michigan Filed Oct. 20, 1965, Ser. No. 498,918 13 Claims.(Cl. 110-101) This invention relates generally to industrial typefurnaces, and more particularly relates to an automatic fuel feedingsystem for use in moist fuel burning furnace, such as bagasse furnaces.

In sugar mills it is convenient and economical to use bagasse as a fuelto heat the steam boilers instead of other known fuels such as oil.While automatic boiler firing control is readily available withconventional fuels such as oil, it has not been fully available withmoist fibrous fuels such as bagasse. In bagasse burning furnaces it hasbeen possible to automatically regulate the boiler outlet damper tomaintain a constant furnace draft and the flow of combustion air to thefurnace in accordance with steam demand, but no automatic means has beenavailable to properly regulate the height of the fuel pile, i.e., thefeeding of the fuel.

Therefore, it is the basic object of this invention to provide a controlmeans to automatically regulate the height of the fuel pile in a moistfuel furnace, such as a bagasse furnace, and thereby, in conjunctionwith automatic regulation of the boiler outlet damper and flow ofcombustion air, enable the same degree of automatic control to beobtained with boilers fired by bagasse as those fired by fuel oil orother fuels.

Being wet, a moist fuel such as bagasse is on the border line betweenbeing combustible and non-combustible. The size, shape, and location ofthe fuel pile are important factors in this connection and indetermining the efiiciency with which the fuel burns. In fact, if thebagasse pile is too high it may topple over and cut off combustion airso that the fire is extinguished. On the other hand, it is desirable tohave the pile as high as possible while still self-sustaining. Thesefactors relate solely to the peculiar nature of the fuel and,accordingly, it is an object of this invention to provide a means forautomatically regulating the feeding of the moist fuel (e.g., begasse)which is responsive to the height of the fuel pile and is independent ofextrinsic factors such as combustion air, furnace draft, or steam flowor demand. By means of such feed regulation optimum burning of the moistfuel is achieved automatically.

There are, of course, many bagasse furnaces now in operation and,accordingly, it is an object of the invention to provide a fuel feedcontrol system that may be readily incorporated into existing furnaceinstallations.

Existing bagasse furnace installations employ a feed chute for each celland, ordinarily, a battery of chutes are fed bagasse by a conveyor orbagasse carrier system. Bagasse flow through each chute is controlled bya gate structure which is moved manually by a handwheel acting throughshafts, bevel gears, pinions, and racks secured to the each slidablehalf of the gate. In accordance with the present invention, it ispreferred to attach a reversible drive motor to the gate operatingstructure and to control the opertaion of the motor by means of asuitable device that senses the height of the fuel pile in the cell.When the pile reaches the desired maximum height the gate opening isdecreased, and when the pile reaches the desired minimum height the gateopening is increased, thus adjusting the flow of bagasse to the cell tomaintain the height of the pile within a desired range. The gate is preferably at least partly open at all times so that there is continuousflow to the cell.

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Other features and objects of this invention will become apparenthereinafter in connection with the description of the accompanyingdrawings in which:

FIGURE 1 is a vertical section through one cell of a moist fuel burningfurnace particularly illustrating the relationship of the feed chutewith the fuel pile and also the relationship of one form of fuel levelindicating device with respect to the fuel pile;

FIGURE 2 is another vertical section through a portion of a bagassefurnace partially illustrating two combustion cells of a three or morecell furnace and particularly illustrating the positioning of the fuellevel indicating devices for an end cell and an intermediate cell;

FIGURE 3 is a representative schematic illustration in front elevationof the operating mechanism for the fuel feed gate control illustratingboth the manual and automatic features of the control apparatus;

FIGURE 3A is an enlarged representative schematic illustration in planview of a fuel gate operator drive train and limit switch arrangementwhich may be utilized in the control apparatus of FIGURE 3;

FIGURE 4 is a side view illustrating the details of a mechanical fuelpile level indicating device and the mounting features thereof, whichdevice may be of the type described in greater detail in U.S. Patent No.2,851,553;

FIGURE 5 is a schematic diagram of control circuitry utilized inconjunction with the fuel indicating device; and

FIGURE 6 is a schematic diagram illustrating the cir- 'cuitry forproviding electrical energy to a magnetic clutch and to the fuel levelindicating device.

Referring to the drawings and first to FIGS. 1-3, there .isillustrated aportion of a moist fuel burning furnace 10 having a horseshoe shapedcombustion cell 11, such as is well known for the burning of bagasse.Generally the furnace comprises a plurality of combustion cells 11, onebeing shown in FIG. 1 and two in FIG. 2, which may be constructed of aslab hearth 12 and a tile wall construction 14. The wall 14 may beconstructed of a series of horizontal courses formed from individualblocks of tile 16 which rest upon a lower course of air passage formingcast iron members 18 and follow the construction and details describedin U.S. Patent 2,694,370 issued Nov. 16, 1964. Fuel for the furnace isfed by means of an inclined fuel chute 20 which is suitably positionedand angled as to provide the proper height and discharge angle for thefuel as it leaves the end of the chute, thereby building up the propersize and shape of the fuel pile 25 on the cell floor 12. Air forcombustion of the fuel is provided by passageways within the wall 14 ofthe cell and is forced therethrough by means of blowers. The gaseousproducts resulting from the burning of the bagasse rises through thethroat 22 and passes over the boiler tubes (not shown) to be heated. Asis seen in FIGURE 1, the furnace may be of the well known Wardconstricted neck design, as is commonly used in applications of thistype. Each cell is provided with a suitable access door 24 to permitentry into the cell.

The size and shape of the fuel pile 25 is sensed by indicator means 28,30, and 30' which extend into the cell in accordance with the particularposition of the fuel chute 20 with respect to the hearth 12. Theindicators illustrated in FIGS. l-4 are of the type shown a? of the pileis directly related to its width each device is responsive to andcapable of providing signals to indicate the height of the pile 25.Preferably, the impeller 32 engages the side of pile on about thecenterline of the pile and at about /3 of its minimum desired heightalong the inclined axis extending at an angle as indicated in thedrawings. While two indicators 28 and 30 are shown in the end cell 11 ofFIGS. 1 and 2 only one of them is actually used and this is preferablydevice 30 which extends through the sidewall 14 rather than theindicator 28 which extends through the door 24. In this left cell ofFIG. 2, the sidewalls are not available for mounting of the indicator30' and it may therefore be mounted in the front wall of the cell, asshown, rather than the door 24.

The indicator devices 28, 30, and 30' are of the type that open andclose a switch with the rotating and stopping of the impellers 32 due toresistance of the pile 25. However, broadly, other types of signallingdevice may be utilized in the practice of the invention to indicate thesizeof the fuel pile 25. For example, an optical system may be usedwherein a beam of light is allowed to shine on a receiving device or iscut off from the receiver, depending on the size and shape of the pile,thereby producing a control signal which is indicative of the conditionof the fuel pile.

As indicated in FIGURE 3, electrical energy from a suitable source issupplied to the indicating device. 30 through a control panel and motorstarter 48 by means of a cable 46. The control signal generated. by theindicator 30 (as well as electrical energy) is fed' from the controlpanel 48 through a cable 52 to a fuel gate operator mechanism 49 whichmay be suitably connected to the conventional rack, pinion, and bevelgear structure 49A that is used to open and close the gate. means 56 forthe chute 20..

The fuel gate operator mechanism 42 has an output shaft 63 that isconnected by means, of the chain and sprocket 55 to an operating shaft58, such as the, pinion shaft of the fuel gate operating structure 49A.Rotation. of shaft 63 in one direction will increase the gate openingand rotation in the opposite directionwill, decrease the opening therebyproviding means for controlling the rate of bagasse flow through thechute 20. Bagasse is fedto the mouth of each chute 20 over th gate means56 by means of a conventional bagasse carrier or conveyor 62.

The fuel gate operating mchanism 49 includes a. reversible motor 50which is connected-througha magnetic clutch 67 to theoutput shaft 63. Bydeenergizing the clutch 67 the motor is disconnected from the gearstructure 49A which may then be manually operated by means of the chainfall 66 which rotates sprocket 68 that is afiixed to the shaft 58. Thus,the gate- 56 can be manually operated or its position can be setasdesired at the time automatic operation commences.

As shown schematically in FIGURE 3A, the gate drive system 49 includesthe reversible motor 50 which is adapted to provide forward and reversepower to its shaft 69 which is connected to a speed reducer 65 .which inturn, is connected by shaft 70 to the. magnetic clutch 67. The shaft 63isdriven by the clutch 67. The drive system includes a pair of rotarylimit switches 71 and 73 to control the length of stroke of the gatemovement and the location of theextreme open and closed positions,respectively, of the gate means 56. These switches therefore provide asimulated modulated control of the fuel flow, it being noted that it isdesirable that at all times the gate means be at least partially openfor fuel passage.

The rotary limit switch 71 has a shaft 77 that is rotated:by the gearreducer shaft 70 through sprockets 75 and 79 and interconnecting chain88. The limits of switch 71 are set to a predetermined number ofrevolutions of the shaft and through suitable electrical circuitrycontrolthe number. of revolutions of shafts 70 and 63 and the length ofstroke of the gate means 56, i.e., the extent of its opening and closingmovement.

The second rotary limit switch 73 has a shaft 8 that is rotated byoutput shaft 63 through sprockets and 39 which are connected together bymeans of a chain 88. The limit switch 73 is initally settodetermine thelocation of extreme open or closed position of the gate 56, i.e., theindexed position of the gate opening. This can be adjusted manually bythe furnace operator from the floor by means of chain 66. When themagnetic clutch 67 is deenergized rotation of shaft 58 by means of thechain 66will rotate shaft 63 and therefore limit switch shaft 87 toreset the switch. Thus, the operator changes the extreme open or closedposition of the gate opening but the length of the stroke of the gateremains fixed by the number of revolutions of shaft 70 as determined byswitch 71. The actual location of the gate opening with respect to thelarger cross sectional area of the chute 29 can affect the flow ofbagasse from the conveyor 62 into the chute, and the switch 73, as justdescribed, enables this to be adjusted at any time in accordance withfuel conditions.

FIGURE 4 illustrates on larger scale one form of indicator device 30referred to above. Additional details are disclosed in US. Patent2,851,553 and the device is available on the open market. The indicatorhas. a rotary impeller 32 which is rotated by a motor in housing 36 and,continues to rotate until the fuel pile has covered the impeller by apredetermined amount, depending on the characteristics of the fuel,whereupon the resistance becomes too great and rotation stops. Insidehousing 36 there is a switch means responsive to torque on the floatinghousing of a synchronous motor driving the impeller so that this, orrotation and stoppage of the impeller, is used to operate the switchmeans and generate a mechanical signal indicative of the height of thepile.

The tube portion 40 of the indicator 30 serves as a housing for shaft 74and threads on an extension 82 of the housing 36 of the motor and signalproducing means. A hearing pin 84 may be provided at one end of the tube40 to provide a bearing surface for the shaft 74 thereby concentricallypositioning the two parts. A mounting sleeve 86 is selectively, slidablymounted on the xterior surface of the tube. 40 and is fixed thereto in adesired position by means of a set screw 88, the screw 88 being adaptedto engage anyone of several longitudinally spaced indented portions (notshown) provided on the tube 40. The sleeve 86 is provided with an angledmounting plate 90 which provides a mounting flange for attachment of theindicator 30 on the wall of the furnace. Suitable holes (not shown) maybe provided in the mounting plate 90 for receiving bolts therethroughfor fastening the plate to the wall of the furnace. By shifting theposition of the sleeve 86 on the tube 40 the immersion depth of theimpeller 32 can be adjusted until it extends into the furnace andbagasse pile 25 to a depth that causes it to stop rotating when thedesired maximum pile height is obtained and resume full rotation whenthe desired minimum height is reached. The signal producing means inhousing 36 comprises any device which will produce a first signalinresponse to the rotating of the impeller and a second signal inresponse. to the stoppage of the impeller (or predetermined maximum andminimum speeds of rotation of the impeller). The signals may take anyform, and, for example, may be a digital or analogue signal or thepresence or absence of a voltage or current, etc. Such a device may be amotor enclosed in a resiliently mounted housing whereby 0 the normalrotation of the impeller closes a first set of contacts and the stoppageof the impeller closes a second set of contacts. This second closing maybe due to the angular movement of the motor housing with respect to theouter casing 36 of the signal means against the bias of a springconnected therebetween. As an alternative, the switching mechanism maycomprise a flyball type switch assembly mounted on the motor shaftwherein a first switch is closed by the governor when the shaft isstopped and a second switch is closed when the shaft is rotating.Reference is made to US. Patent 2,851,553 for a suitable motor andsignal producer for impeller 32.

Referring now to FIGS. 5 and 6, there is illustrated a schematic diagramof a suitable circuit interconnecting the parts of the fuel controlsystem described above and forming the control panel 48. The reversiblemotor 50 is supplied with three-phase alternating current by means ofconductors 192, 104, and 166 which is fed through a set of contactors108, 110, and 112 and conductors 114, 116 and 118 to the motor. Thereversing function is performed by a second set of conductors 120, 122and 124 and a second set of contactors 126, 128, 130 which reverses twoof the phases with respect to the third phase thereby reversing therotation of the motor when the second set of conductors is energized.The control circuitry for the two sets of contactors is connected acrossconductors 104 and 1&6 and generally comprises a switching mechanism 134which is contained within the signal producing means in housing 36, thelimit switch 73, the limit switch 71, and the coils for the two sets ofmotor starting contactors 138. Also a normally open start-stop contactor149 is provided to control the manual or automatic operation of thesystem. When contactor 140 is opened, the automatic portion of thesystem is disabled thereby allowing the manual operation of the gatemeans 56.

The signal producing means in housing 36 contains the switch 134 whichhas an armature or blade 142 movable between a pair of terminals 144 and146. When the impeller is rotating the blade 142 is in contact withterminal 144 and when it has been stopped the blade 142 is in contactwith terminal 146. Terminal 144 is connected to a contactor 148 by meansof conductor 147, contactor 148 being part of rotary limit switch 71which is set to a predetermined number of revolutions of shaft 70 todetermine the length of the travel or stroke of the gate openingmovement. A relay coil 150 is also connected in series circuit with thelimit switches 71 and 73 including a contactor 151 by means ofconductors 152 thereby energizing the coil 1513 at such time as theswitch 142 is in contact with terminal 144 and the feed gate is inclosed position thereby closing contacts 148 and 151. A coil 1:56 and apair of contactors 158 and 159 are connected in series circuit betweenthe terminal 146 at one end thereof and the contacts 140 at the otherend and in parallel circuit to contacts 148 and 151 and coil 15%.

The contactors 158 and 159 provide a limit switch function limiting theclosing movement of the feed gate so that it is open at least a minimumamount to feed a small portion of fuel to the furnace at all times,preferably about 15% of the rate at which the fuel is burned. The coil150 is operatively associated with contactors 108, 110 and 112 to closethese contacts when actuated, thereby energizing the reversible motor ina first direction to open the feed gate. Similarly, coil 156 isoperatively associated with contactors 126, 128 and 130 to reverse theoperation of the motor 1019 thereby moving feed gate 56 toward closedposition reducing the flow of fuel to the cell to the desired minimumrate, (e.g., the 15% referred to above).

In operation, and assuming that the fuel gate is open and fuel is beingfed by gravity from chute 20 into the combustion cell of the furnace,the contacts 148 are open and the switch blade 142 is in contact withterminal 144 due to the fact that the shaft of the signal means 36 isrotating. When sufiicient fuel has been fed to the furnace, the impeller32 will be stopped and the switch 134 will shift to the position whereinblade 142 is in contact with terminal 146. Thus, the coil 156 will 6 beenergized thereby closing the contacts 126, 128, to reverse theoperation of the motor and reduce the fuel gate opening. When the fuelgate has closed sufliciently to activate the limit switch 71 (or 73 ifit is set for extreme closing) and open either of selected contactors158, 159, the motor 51) will then be stopped.

As the fuel is being burned down, the fuel pile will recede from theblades of the impeller section 32, and at such time as the fuelresistance is reduced sufliciently the impeller will resume rotation.With the gate 56 in the near closed position, the contacts 148, 151 willbe closed, the switch blade 142 will be in contact with terminal 144,and the coil 15% will be energized thereby closing contacts 108, 110 and112, With these latter contacts closed, the motor 160 will again reverseand open the feed gate until such time as the limit switch 71 (or 73 ifit is set for extreme opening) is activated to open contacts 148 or 151.This cycling is repeated during the entire combustion of the fuel pile.When it is desired to deenergize the system, contacts are opened and thecontrol portion of the system will be deenergized.

Referring to FIG. 6, there is illustrated a schematic diagram of asystem for feeding electrical energy to the magnetic clutch of the motorand also the windings or other devices within the indicator 30. Theindicator could be driven by a synchronous motor type, the hysteresismotor type, or any other suitable means for providing the switchingfunction as described. In most of these switching arrangements, a sourceof electrical energy is required and thus a source 166 of alternatingcurrent energy is connected to the active portion 162 of the signalmeans in housing 36 by means of a pair of conductors 164, 166 and 168,170. As was described above, the motor 50 illustrated in FIG. 3A, isprovided with a magnetic clutch 67 to couple and decouple the motor fromthe operating mechanism 49 and the feed gate 56, and this clutch 67 isalso fed from the source 160 through conductors 164, 166 and a pair ofcontactors 174 and 176. The contactors 174 are magnetically connected tothe coil and the contactors 176 are magnetically connected to the coil156, Thus, the magnetic clutch is energized whenever the motor 50 isenergized in either direction, thereby coupling the motor to the feedgate. As an alternative arrangement, the contactors 174, 176 may becombined into a single contact in the control panel 48, and thus themagnetic clutch will be continuously energized as long as the automaticsystem is being used. However, if it is decided to resort to manualoperation, the single contact may be opened.

While the above invention has been described with an electromechanicalindicating means 30, it is to be understood that other suitable types ofsignal producing indicating means may be utilized. One such indicatingmeans is a modulated type beam indicator in the walls of the furnace toprovide a beam of light which will be broken by the fuel pile when ithas reached the prescribed size. In this latter case the transmitterportion of the optical system comprises a projector with two focusinglenses, a light source, and a motor driven aperture disc; and thereceiver comprises a pair of lenses, a photocell, an amplifier andcontrol output relays. The beam indicator employs a modulated signalbeam which is unaffected by extraneous light, falling particles, flameor smoke. The two signal beams are stacked, one on top of the other, ineach of the projector and receiver. By successive interruption of thetop beam and clearing of the bottom beam, a control signal is providedto regulate the control system and thus the fuel gate operator in amanner similar to that described in conjunction with electromechanicalsystem above.

It will now be seen that the invention provides an automatic bagasse ormoist fuel feed system in which the bagasse is continuously fed bygravity to the cell at a minimum rate which is below the rate of fuelconsumption and at a maximum rate which is greater than the rate of fuelconsumption, the rate of flow being controlled by an indicator means 30which is sensitive directly or indirectly only to the height of the fuelpile. The indicator means is set to maintain the height of the bagassepile between levels that provide optimum combustion of the fuel.

While it will be apparent that the embodiment of the invention hereindisclosed fulfills the objects of the invention, it will be appreciatedthat the invention is susceptible t-o modification without departingfrom its spirit and scope.

I claim:

1. The method of supplying fuel to the hearth of a moist fuel combustioncell which comprises feeding'moist fuel continuously through a partiallyopen gate to a gravity feed chute which deposits the fuel in a pile onthe hearth, sensing the height and location of portions of the sides ofthe pile of fuel with a signal producing means and using the signal toopen said gate wider when the height falls to apredetermined minimum,and sensing the height of the pile with a signal producing means andusing the signal to at least partially close the gate when the height ofthe pile reaches a predetermined maximum.

2. The method of supplying fuel to the hearth of a moist fuel combustioncell which comprisesfeedingmoist fuel through a movable gate controlledopening to a gravity feed chute which deposits the fuel in a pile on'thehearth, sensing the height and location of portions of the sides of thefuel pile with a signal producing means and usingthe signals produced bysaid means to control the position of the movable gate and the size ofthe gate controlled opening and therefore the rate of fuel supply to thechute.

3. A moist fuel burning furnace having a hearth for supporting a fuelpile, a chute for supplying the fuel to the hearth in a pile, a fuelgate for controlling the flow of fuel to the chute, and a fuel feedingcontrol system comprising signal producing indicating means for sensingthe size and location of portions of the sides of the fuel pile, saidindicating means producing a signal having a characteristic inaccordance with the size of the pile, means operatively connected to thefuel gate and responsive to the signal of said indicating means forcontrolling the operation of the fuel gate, and control means energizingsaid fuel gate operating means in accordance with said signalcharacteristic.

4. A moist fuel burning furnace having a hearth for supporting a fuelpile, a chute for supplying the fuel to the hearth in a pile, a fuelgate for controlling the fiow of fuel to the chute, and a fuel feedingcontrol system comprising signal producing indicating rneanis forsensing the height and location of portions of the sides of the fuelpile, said indicating means producing a signal having a characteristicin accordance with the height of said pile, a reversible motoroperatively connected to the fuel gate to move the gate and responsiveto the signal of said indicating means, and control means energizingsaid motor in one or the other direction in accordance With said signalcharacteristic.

5. A moist fuel burning furnace having a hearth for supporting a fuelpile, a chute for supplying the fuel to the hearth in a pile, a fuelgate for controlling the flow of fuel to the chute, and a fuel feedingcontrol system comprising signal producing indicating means for sensingthe size of the fuel pile, said indicating means having a reversingswitch for producing a signal having a characteristic in accordance withthe size of said pile, a reversible motor operatively connected to thefuel gate and responsive to the signal of said indicating means, andcontrol means including a first coil and a first set of contactors forenergizing said motor in a forward direction and a second coil and asecond set of contactors for energizing said motor in a reversedirection, said coils being selectively energized in accordance withsaid signal characteristic, said control means including disconnectmeans for disabling said control means for providing manual operation ofsaid fuel gate.

6. The invention of claim 5 wherein said disconnectmeans includes amagnetic clutch operatively associated with said first and second coilfor interconnecting said motor and said fuel gate.

7. The invention of claim 5 wherein said indicating means includes animpeller to be embedded in the fuel pile, and motor driving saidimpeller and having a floating housing and said reversing switch beingselectively operated between two positions in accordance with the torqueon said housing.

8. A fuel burning furnace having a hearth for supporting a fuel pile,chute means for supplying the fuel to the hearth in a pile, a fuel gatefor controlling the flow of fuel to the chute means, and a fuel feedingcontrol system comprising signal producing indicating means for sensingthe size of the fuel pile, said indicating means having. a. reversingswitch for producing a signal. having a characteristic in accordancewith the size of, said pile, a reversible motor operatively connected tothe fuel gate and responsive. to the signal v of said indicating, means,control means including a first coil and a first set of contactors forenergizing said motor in a forward direction and a second coil and asecondset of .contactors for energizing said motor in a reversedirection, said coils being selectively energized in accordance withsaid signal characteristic, and limit circuit means for selectivelycontrolling the open and closed positions of the fuel gate includingfirst andsecond switch means connected in circuit controlling relationwith said coils for controlling the energization of the coils inaccordance with the position of the fuel gate and the length of strokeof the fuel gate.

9. The invention of claim 8 including manually operated remote settingmeans for adjusting the setting of said first switch means to adjust theindexed position of the fuel gate.

10. A moist fuel burning furnace having a hearth for supporting a fuelpile, a chute for supplying the fuel to the hearth in a pile, a fuelgate for controlling the fiow of fuel to the chute, and a fuel feedingcontrol system comprising signal producing indicating means for sensingthe size of the fuel pile, said indicating means having a reversingswitch for producing a signal having a characteristic in accordance withthe condition of said pile, a reversible motor operatively connected tothe fuel gate and responsive to the signal of said indicating means, andcontrol means including a first coil and a first set of contactors forenergizing said motor in a forward direction and a second coil and asecond set of contactors for energizing said motor in a reversedirection, said coils being selectively energized in accordance withsaid'signal characteristic, said indicating means including switch meansbeing selectively connected in series circuit with one of said first andsecond coils in accordance with said signal characteristic.

11. The fuel burning furnace of claim 10 further including a magneticclutch interconnecting said reversible motor and the fuelgate, means forselectively energizing and deenergizing said magnetic clutch, and manualmeans connected to the fuel gate for manually controlling the fuel gatewhen said magnetic clutch is deenergized.

12. The method of supplying bagasse or the like to a combustion cellhaving a floor during operation of the cell comprising continuouslydepositing the bagasse in a pile on the floor at a first ratesubstantially less than the rate of bagasse consumption by combustion inthe cell, sensing the height and location of portions of. the sldes ofthe bagasse pile, and increasing the rate of deposition of bagasse togreater than the rate of fuel consumption when the height of the pilereaches a predetermined minimum and continuing such increased rate untilthe height reaches a predetermined maximum and then returning to saidfirst rate of deposition.

13. A moist fuel burning furnace having a hearth for supporting a fuelpile, a chute for supplying the fuel to the hearth in a pile, a fuelgate for controlling the flow of fuel to the chute, and a fuel feedingcontrol system comprising signal producing indicating means for sensingthe height and location of portions of the sides of the fuel pile, saidindicating means producing a signal having a characteristic inaccordance with the height of said pile, a reversible motor operativelyconnected to the fuel gate to move the gate and responsive to the signalof said indicating means, and control means energizing said motor in oneor the other direction in accordance with said signal characteristic,indicating means including rotatable impeller which is embeddable in thefuel pile,

10 said signal being one of rotation and non-rotation of the impeller.

References Cited UNITED STATES PATENTS 2,114,619 4/1938 Ward l10-10 X2,299,727 10/ 1942 Blauvelt et al 1l010l 2,426,347 8/1947 Fulton 110101X FOREIGN PATENTS 463,003 7/ 1928 Germany. 396,039 7/ 1933 GreatBritain.

KENNETH W. SPRAGUE, Primary Examiner.

5. A MOIST FUEL BURNING FURNACE HAVING A HEARTH FOR SUPPORTING A FUELPILE, A CHUTE FOR SUPPLYING THE FUEL TO THE HEARTH IN A PILE, A FUELGATE FOR CONTROLLING THE FLOW OF FUEL TO THE CHUTE, AND A FUEL FEEDINGCONTROL SYSTEM COMPRISING SIGNAL PRODUCING INDICATING MEANS FOR SENSINGTHE SIZE OF THE FUEL PILE, SAID INDICATING MEANS HAVING A REVERSINGSWITCH FOR PRODUCING A SIGNAL HAVING A CHARACTERISTIC IN ACCORDANCE WITHTHE SIZE OF SAID PILE, A REVERSIBLE MOTOR OPERATIVELY CONNECTED TO THEFUEL GATE AND RESPONSIVE TO THE SIGNAL OF SAID INDICATING MEANS, ANDCON-